Hello Instructables community! In this Instructable I will show you how to make a folding ring knife. This knife is made from scrap aluminum and an old saw blade. This folding ring knife has a regular knife and a sawing knife. I do not have any kind of jeweler's tools so this is all made from stuff I already had in my garage. The original idea came from Miller Knives tutorial for making a folding ring knife. I made a few changes to the design, but the assembly is pretty much the same. Remember to be safe!
Step 1: Gather the Materials
Aluminum (The dimensions for my piece were 1-1/2" wide, 2" long, and 5/8" thick)
Bench grinder (I used a coarse grinding wheel and a brass wire wheel)
Drill bit that is the same diameter as your ring size (I used 3/4" drill bit and it fit perfectly)
Drill bit that is the same diameter as the nails you are using (For me, this was a 5/64" drill bit)
Rotary tool or Dremel
Fiberglass reinforced cutting disk for the rotary tool or Dremel
Round file (Only if your ring hole isn't big enough)
Sharpie or other way to mark metal
Step 2: Making the Ring
First, take your piece of aluminum. Find the center of it and then mark a little bit down from the center. Make sure there is still enough room for the "walls" on the ring. Drill a hole the same size as your finger. I started by using a 3/8" high speed metal drill bit and then worked my way up to a 3/4" drill bit I used for another project. If you have to, use the round file to make the hole a little bigger to get the hole to the correct size you want. The 3/4" hole was big enough for me, so I just left it the way it was. Next, you want to cut off the corners near the hole. Then you can clean it up with the grinder to make it all even and smooth. Now use the hacksaw to make notches in the ring. This was about an inch for me. Do not cut all the way through the ring because this is where the knives will be. Then use the rotary tool with the cutting disk attached to it and move it around inside the notches. Do not use too much pressure or else it will break the disk. Then use the half round file and make an indentation where the notches are. Make sure it is going the opposite direction of where the notches are going.
Step 3: Making the Knife Stock
Take the saw blade and cut about an inch off of it. Do this two times so you end up with two pieces of saw blade. Unless you're hacksaw and saw blade are the same size, you'll need to flatten the knife stock more. I did this by grinding the knife stock on the side of the grinding wheel. You need to do this on both pieces of knife stock. I did this by attaching the knife stock to the vise grips and just kept grinding the knife stock on the flat side of the grinding wheel until it was thin enough to fit into the notch on the ring. One good way to make sure you get an even grind is to look at the colors of the steel as it heats up. The more you grind, the hotter the knife stock gets. Once it starts to get hot enough, steel changes colors. You can use the different heat colors to make sure everything is even. When both pieces of knife stock fit into the notches, put both of them into the notches. Next, drill a hole into the corner of the ring. The drill bit should go through the ring and both knives. Now you have a hole in the knife stock and ring. This is where the nail will go through to act as a rivet. You have now finished making the knife stock.
Step 4: Making the Knife
First you want to cut off the extra material from the knife stock. Make sure you put a nail through all of it to make sure it all lines up. Then mark it and cut the extra material off. Draw the shape of the knife you want to make onto the knife stock. Then use the grinder and grind the shape you want. Put everything together with the nail to make sure it opens correctly. If the blade doesn't open, it is probably because you have some extra material at the bottom of the blade. To fix this, slowly take off material at the bottom of the blade. Now make the finger notch. All you need to do is use the rotary tool with the cutoff disk and slowly move the disk side to side until you make a notch. If you want to heat treat the knives, there are plenty of instructables on how to do it. I chose not to heat treat this time, because I wasn't going to be using this knife for anything significant.
Step 5: Riveting
Once you finish making the knife, put it all together. Put the nail through the hole and cut off the extra material from the nail using the bolt cutters. Then hit the end of the nail with a hammer until it mushrooms out. This will make a head on both sides of the nail. You have finished the Folding Ring Knife! If it is hard to open, put some WD-40 into the notch to help lubricate it and make it easier to open. Remember to be safe!